The invention refers to a device for equalizing the warp yarn tension in a loom having a movably supported back rest.
For equalizing the warp tension during the weaving process, especially during formation of the shed and during beat up of the reed, it is usual to arrange the back rest of the loom to be movable. In that case, three fundamental suspension systems are known. On the one hand, spring members are provided in the back rest suspension, the action of which is directed against the force exerted by the warp. On the other hand, the back rest is rigidly supported in a suspension which is moved positively in the direction of a yielding of the warp in time with the formation of the shed or with the beat up of the reed respectively. Finally, combinations of both systems are also know, in which the back rest is supported springily in a suspension moved positively and in time with the formation of the shed or the beat up of the reed respectively. All of the systems have the disadvantage in common, that the back rest suspension engages with the side frames of the loom at two points.
Since the warp force is distributed more or less uniformly along the length of the back rest from the sum of the forces from the individual warp threads, this two-point support demands a back rest resistant to bending with a corresponding weight, which is in the way of the above-mentioned movements for equalizing the warp tension.
Complete equalizing of the warp tension without the occurrence of peaks in the tension is thereby rendered substantially impossible.